Multi-Carrier In General
A multi-carrier system which will be described hereinafter illustrates a case where one or more individual carriers are bundled to be used. FIGS. 1A and 1B are views for describing a multi-band radio frequency-based signal transmission and reception method.
Technologies in which multiple carriers (for example, multiple frequency allocation (FA) bands) are managed by one medium access control (MAC) entity to effectively manage a multi-band (or multi-carrier) have been proposed.
In FIG. 1, one MAC layer at the transmission and reception ends can manage multiple carriers to effectively use a multi-carrier. At this time, in order to effectively transmit and receive a multi-carrier, it is assumed that both the transmission and reception ends can transmit and receive a multi-carrier. At this time, frequency carriers (FCs) managed by one MAC layer allows flexible resource management since they do not need to be contiguous.
In other words, the frequency carriers may have contiguous aggregation or non-contiguous aggregation.
In FIGS. 1A and 1B , PHY 0, PHY 1, . . . , PHY n-2, and PHY n-1 represent multiple bands according to this technology, and each band may have a frequency allocation (FA) size allocated for a specific service according to a predetermined frequency policy.
For example, PHY 0 (RF carrier 0) may have a frequency allocation size allocated for a general FM radio broadcast, and PHY 1 (RF carrier 1) may have a frequency allocation size allocated for cellular phone communication.
In this manner, each frequency band may have a different frequency allocation size depending on the characteristics thereof, but it is assumed in the following description that each frequency allocation (FA) has a size of A MHz for the sake of convenience of explanation.
Furthermore, each frequency allocation may be represented by a carrier frequency to use a baseband signal in each frequency band. Thus, in the following description, each frequency allocation will be referred to as a “carrier frequency band” or will be simply referred to as a “carrier” representing each carrier frequency band if it does not cause confusion.
Furthermore, as in the recent 3GPP LTE-A, the foregoing carrier may be referred to as a “component carrier” to discriminate it from a sub-carrier used in the multi-carrier scheme.
In this aspect, the foregoing “multi-band” scheme be may also referred to as a “multi-carrier” scheme or “carrier aggregation” scheme.
In order to transmit signals through multiple bands as illustrated in FIG. 1A and receive signals through multiple bands as illustrated in FIG. 1B, both the transmitter and receiver are required to include an RF module for transmitting and receiving signals through multiple bands. Furthermore, in FIG. 1, the configuration method of “MAC” is determined by a base station, regardless of downlink (DL) or uplink (UL).
For the sake of convenience of explanation, this technology is a scheme in which one MAC entity (hereinafter, simply referred to as a “MAC” unless if it does not cause confusion) manages and operates a plurality of radio frequency (RF) carriers to transmit and receive signals. Furthermore, the RF carriers managed by one MAC are not required to be contiguous. As a result, according to this technology, it has an advantage of flexibility in terms of resource management.
In an IEEE 802.16m system, which is one radio communication systems, the carrier type can be largely divided into two kinds of groups in the aspect of a base station. For example, it may be divided into a fully-configured carrier type (hereinafter, “FCCT”), and a partially-configured carrier type (hereinafter, “PCCT”).
The fully-configured carrier type represents a carrier capable of transmitting and receiving both control information and data, and the partially-configured carrier type represents a carrier capable of only transmitting downlink (DL) data. At this time, the partially-configured carrier may be used for a service, such as an Enhanced Multicast Broadcast Service (E-MBS), mainly providing downlink (DL) data.
The carrier allocated in the aspect of a mobile terminal can be divided into two carrier types. For example, the carrier type may be divided into a primary carrier and secondary carriers. At this time, one primary carrier and a plurality of secondary carriers may be allocated to mobile terminals from a base station.
The primary carrier is selected from fully-configured carriers, and most main control information of a mobile terminal may be transmitted on a primary carrier. The secondary carrier may be selected from fully-configured or partially-configured carriers, and may be additionally allocated according to the mobile terminal or base station's request or instruction.
The mobile terminal may transmit and receive control information on a secondary carrier as well as all control information through a primary carrier, and the mobile terminal may transmit and/or receive data to and/or from the base station through a secondary carrier. At this time, the secondary carrier as a fully-configured carrier allocated to a specific mobile terminal may be configured as the primary carrier of another mobile terminal.
Multi-Carrier Switching
It refers to a multi-carrier mode in which a terminal switches its physical layer connection from a primary carrier to a partially-configured or fully-configured secondary carrier. Here, the carrier switching of a terminal is carried out by an instruction of the base station to receive an Enhanced Multicast and Broadcast Service (E-MBS) in a secondary carrier.
The terminal is connected to a secondary carrier for a specific period of time, and then the connection returns to a primary carrier. The terminal is not required to maintain its transmission or reception through a primary carrier while the terminal being connected to a secondary carrier for a specific period of time.
Basic Multi-Carrier (MC) Mode
Basic multi-carrier mode refers to a mode in which the terminal is operated with only one carrier. However, the terminal supports a primary carrier change process as well as an optimized scanning for carriers associated with the multi-carrier operation.
Carrier Switching Operation For E-MBS Services
E-MBS services are carried out by a specific carrier (secondary carrier), which is not a primary carrier of the terminal. An E-MBS terminal (a terminal being operated in a carrier switching mode) having only one transceiver in a state of being connected to the base station is switched from a primary carrier to another carrier to receive E-MBS data bursts, an E-MBS configuration message, and an E-MBS MAP, and performs carrier switching from the another carrier to the primary carrier to receive a unicast service from the base station.
The E-MBS terminal performs a carrier switching operation based on the terminal's E-MBS subscription information allocated from the base station to the terminal during a dynamic service addition (DSA) process. For example, the E-MBS subscription information may be MSTIDs+FIDs.
FIG. 2 is a view illustrating a method of performing a carrier switching operation for allowing the terminal to receive an E-MBS service when the terminal's carrier switching mode is activated in a multi-carrier system.
If the terminal's carrier switching mode is activated, then the terminal may receive a unicast service through a primary carrier during the unicast available interval.
The terminal may transmit uplink data to the base station through a primary carrier during the unicast available interval, and may perform an uplink HARQ retransmission process. The information on the unicast available interval may be transmitted by the base station.
Furthermore, the terminal may receive E-MBS data such as E-MBS contents, an E-MBS MAP, an E-MBS configuration message, and the like, from the base station through a secondary carrier in which an E-MBS service is transmitted during the remaining interval excluding the unicast available interval.
As illustrated in FIG. 2, if the unicast available interval is terminated, then the terminal performs carrier switching from a primary carrier to a secondary carrier to receive an E-MBS service through the secondary carrier during the E-MBS service interval. Furthermore, if the E-MBS service interval is terminated, then the terminal performs carrier switching from a secondary carrier to a primary carrier to receive a unicast service from the base station through the primary carrier.
UL HARQ Operation
In a 16 m system, an uplink HARQ process is synchronously operated in general. In other words, if the uplink HARQ process is operated, then resources for retransmission are allocated to LRUs such as previous HARQ subpacket transmission of one sub-frame subsequent to an indicated period (HARQ timing specified in the system).
The operation is applicable to a case where UL Basic Assignment A-MAP IE is not transmitted at the relevant timing, and resources for retransmission is allocated to LRUs indicated by the relevant UL Basic Assignment A-MAP IE if the UL Basic Assignment A-MAP IE is transmitted for HARQ retransmission. The resource allocation for retransmission to such one HARQ process is implemented until the maximum number of HARQ transmissions specified by a system is terminated.